It doesn't matter at this stage, your FEO can amend it for you without you having to pay for another variation. Most FLO's will put expanding ammo on by default if you put Vermin/Pest control as your reason for wanting a FAC but it's worth mentioning to him to make sure.
My FEO had only been in the job a few days when he came to see me and I'd put ".22 HP" on my application, he asked me what it meant and I said Hollow Point, he said I'd probably not get that on first cert and have to wait until renewal but the FLO over-ruled him and said they put expanding on by default, even if you don't